I bought a refurbished Dyson on eBay for around £120. The battery had been replaced and it came with all the attachments. It’s great for keeping the boat clean.
Dirt Devil handy zip is the best very small vacuum. It has a brush roller to aid collection. Sadly they are no longer made but many still come up on Ebay for around the £20 mark. The replacement model is total rubbish in every way.
I have a Hoover with electric brush that works as well as a 220V unit but only 20 min battery life. I bought a spare battery so one is always on charge. ~100 quid.
Following on from my earlier suggestion of a Dyson, I did have an issue with my house Dyson where it developed a battery fault within the first year. The lady in the call centre was very helpful and arranged to get a replacement battery sent to me. She did recommend me to never plug in the Dyson when it has just been used as the battery will be hot. This degrades the battery very quickly, never had an issue since.
The hose was quite short and it fell over, yet again... while stretching into the bilge spillng its load of oily bilgewater all over me... words were had!
Similar idea to Scarron, although a rechargeable one (batteries). It’s extremely powerful and has all the attachments you could need. The ‘wet’ capability is brilliant. It’s a real workhorse all over the boat and is a cinch to store. I baulked a bit at the initial price (around £150), but it’s earned its keep and is built like the proverbial brick outhouse.